An F/A-18 fighter jet and a KC-130 tanker plane belonging to the U.S. Marines collided and crashed off Cape Muroto of Japan's western coast early on Thursday, with six of the seven crew members still missing, the U.S. Marines and Japanese Defense Ministry said.

According to officials, there were two crew members aboard the fighter jet and five crew members aboard the tanker plane when the collision occurred at around 1:40 a.m. local time.

According to Japan's Defense Ministry, one person has been rescued by the Japanese Self-Defense Forces (JSDF).

The rescued crew member was taken to the Marine Corps Air Station Iwakuni in western Japan, the Marines said, while a Japanese official stated that the person who was rescued by the JSDF, is in a stable condition.

The ministry said the planes, based at the Marine Corps Air Station Iwakuni in western Japan, were conducting a routine training operation when the collision occurred around 100 km south of Cape Muroto in Kochi Prefecture.

There is speculation the F/A-18 fighter jet was refueling midair when the collision with the KC-130 tanker took place, although there has been no official confirmation of this as yet.

Mid-air refueling can be a tricky process especially at night and in inclement weather, aviation experts said of the matter.

A JSDF search and rescue aircraft was quickly deployed to help with rescue efforts, while other SDF aircraft and vessels are also searching the area for survivors, the Marines said.

The Japanese Defense Ministry is currently trying to ascertain more details from the U.S. forces in Japan about the accident, which is currently under investigation.

The latest U.S. aircraft mishap comes on the heels of another F/A-18 fighter aircraft, this one belonging to the USS Ronald Reagan nuclear carrier, crashing into the Pacific Ocean in waters southwest of Kita Daitojima Island around 290 km from Okinawa, owing to mechanical issues, on Nov. 12.

Both pilots in this incident managed to eject to safety and were rescued by a U.S. military chopper.

The crash of the F/A-18 aircraft, a multirole combat jet, designed as both a fighter and attack aircraft and known colloquially as the "Hornet," also comes on the heels of a U.S. Navy MH-60 Seahawk helicopter crashing on the deck of the USS Ronald Reagan on Oct. 19 during routine operations.

The crashes occurring within a month of each other and related to the same aircraft carrier, sparked a great deal of concern from the Japanese government, who said it will strongly request information about the accident amid safety concerns and local citizens' fears.

Chief Cabinet Secretary Yoshihide Suga said at the time that accidents "involving U.S. military cause immense worry to people in the area and should not occur."

Japan's top government spokesperson at the time vowed to "strongly request that the United States provide us with information and ensure absolute safety management."